Failure prediction of IGBT modules based on power cycling tests

This article describes a possible method to assess the long-time behaviour of IGBT modules using the combination of power cycles to stress the devices and thermal transient testing to monitor possible die-attach degradation. The failure of an IGBT module is a complex phenomenon; it consists of thermal, electrical and thermo-mechanical effects. After a theoretical overview of the possible mechanisms, a detailed description on the structure of selected IGBT module and the power cycling parameters is given. To better understand the temperature distribution on the device and the reason of the failure after the cycling, the module was opened up, inspected visually and an equivalent thermal model was built and calibrated to the physical test results. Failure mechanisms such as die attach resistance increase, wire bond cracking and gate oxide degradation were detected.